Rotor -- in a gas turbine engine, the turbine wheel.
Scavenge oil system -- method of returning oil from the engine to the oil tank, for cooling and reuse.
Scavenger pumps -- those that drain oil from the sumps at various parts of the engine, return it through
the oil cooler, and back to the oil tank.
Secondary air -- large surplus of air that cools the hot sections of a gas turbine engine to lower
temperatures.
Shaft horsepower (SHP) -- energy used to drive the compressor and accessories in a turbine engine.
Shroud -- device used with turbine rotor to prevent blade tip losses and excessive vibrations. The
shrouded blades can be thinner than unprotected ones.
Simplex nozzles -- single-orifice channels through which highly atomized and accurately shaped sprays of
fuel go into the combustion chamber.
Solvent immersion -- cleaning method in which parts are immersed in solvent to remove carbon, gum,
grease, and other surface contaminants.
Splines -- teeth in a gear.
Speed governor -- device to relieve the pilot from resetting the power lever when outside air temperature
and pressure change. Consists of flyweights balanced by a spring.
Standard day conditions -- 59F, sea level barometric pressure (29.92 inches of mercury).
Stator -- part of assembly that remains stationary with respect to a rotating part. Stator vanes are a
stationary set of airfoils in a compressor.
Tachometer -- device that gives the pilot a continuous indication of engine rpm.
Tachometer generator -- device that supplies power at a frequency proportional to the driven speed
which drives the synchronous motors in the indicator.
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